Lock for self-packing pistons



S. B. REDFIELD LOCK FOR SELF PACKING PISTONS Feb. 14,1928.

Filed July 15. 1926 i \Q [A r 5 v 1 1 T U u U INVEN/TOR $076.13 a'fz H15 AT ORNEY.

reamed Feb.14,1928.

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Application as July 15, 1926. Serial no. 122,715;

This invention relates to pistons, but more particularly to a lock for pistons of the selfpacking type. I I

The objects of the invention are to prevent leakage of pressure fluid between the piston and its cylinder,.to prevent separation of the parts comprising the piston and to insure free relative movement of such 7 parts. r

Other objects will bcin part obvious and in part pointed out hereinafter.

The invention consists of the combination of elementsand arrangement of parts having the general mode of operation substanw tially as described hereinafter and more par-' ticularly pointed out in the appended claims and illustrated in the accompanying drawmg. The figure in the drawing is a sectional elevation of a compressor unloader equipped with a piston constructed in accordance with the practice of the invention.

Referring to thedrawing in which is illustrated one form which the invention may assume in practice, apiston d is provided with an external flange e of substantially the same diameter as the chamber. f of the cylinder 0 and a body portion 9 of the piston d is adapted to cooperate slidably with a bore h of a reciprocable piston head j slidable in the chamber f. A cover plate 70 forms a closure for the end of the cylinder f and this cover may be secured in position by tap bolts olas indicated. Pressure fluid for actuating the piston head j, the the piston (Z and consequently valves U and H, is conveyed thru a pipe to the chamber f. v y

Means is provided for preventing separation of the piston head 7' and the piston (Z. To thisend an external annular groove 9 is formed near the end of the bodyportion 5 of. the piston d to receivean expansible spring ring 0* which cooperates slidably with an internal annular groove 8 formed in the rearward end of the piston head j. The groove 8 is PIBiEBIELblYOf considerable width so as to permit a rather wide range of relative longitudinal movement between the piston d and the piston head j for the purpose of compressing the packing to interposed between the flange e and attend V of the piston head 7' for the purpose of rendering the entire piston assembly leak-proof when piston assembly.

held stationary in'the position shown and 5; yet ea'silyslidable to open the valve H upon removalot pressure fluid from the chin;- ber 7. o

By means of the present invention, the parts which comprise the means for cornpressing the packing, that is, the piston d and the piston head may at all th es he held eflectively against separation with re spect to each Oil'lCl'. There are no loose parts which may be vibrated out of assen bled position and lost as so irequentl; m:- curs where the mechanisn'i of wl'iich 'l'orm a part is subjected. to extren'iely n usage. Furthermore, it is in'ipossihle, by means of this lock, to apply an excess (piantity of packing a, through mistahdwhich would thereby so lengthen the piston assembly that the valve H might not be opened. In assembling the piston (Z in the piston head 9', the spring ring r'may be placed in the' annular groove g and the piston me then be inserted into the piston head j and pushed thereinto until the spring ring r passes the shoulder t in the piston head. The spring ring will then expand and the parts will be held thereby against separation. After the piston and the piston head have been thus assembled, the packing a may be interposed between the flange e of the piston and the end n of the piston head and 65 the entire, assembly willbe in readiness to be placedin the cylinder chamber 7, Subsequent replacei'nents oi the packing to nni'y be readily made since itis merely newssary vto remove the cover plate K: from the cylinder 0 and the piston assembly may then. be removedfrom thecylinder o and new pacl-tingsupplied thereto in the manner described Without necessitating the dismantling of the A suitable application for the sell"? packing; piston above described is illustrated in the drawing wherein is provided a valve T adapted to be held seated by the pressure transmitted thru the piston cl. The valve T is arranged to control the flow of fluid from a passage B to a passage E, both passages being formed in a body A.

I claim: p i

1. In a self-packing piston, the combination of a cylinder, a pressure fluid actuated pistonhead in the cylinder a piston slidahle in-the piston head, an external flange on the piston, packing between the flange and the end of the piston head to prevent leakage of pressure fluid from the cylinder, and a spring ring carried by the piston to cooperate With the piston head for limiting rela? tive longitudinal movement between the piston and the piston head.

2. In a self-packing piston, the combination of a cylinder, a pressure fluid actuated piston head in the cylinder having an internal annular groove, a shoulder at one end of the groove, a piston slidable in the piston head, said piston having an external SNOWVDEN B. REDFIELD. 

